The invention relates to a method for adjusting the picture definition on the camera lens of a motion picture camera and to an apparatus for carrying out the method.
It is known to connect a follow focus, which is operated manually by a focus puller in order to relieve the cameraman, to the camera lens in order to adjust the picture definition and to focus images to be recorded or sequences to be recorded by motion picture cameras. Either the follow focus is connected mechanically to the lens ring for adjusting the picture definition of the camera lens, or a drive unit, which is operated by an electric motor and arranged horizontally or vertically on the camera lens, uses a toothed pinion to transmit a torque to the external teeth of the picture definition lens ring for sharp focusing according to EP 0 575 022 B1.
At the same time, the drive unit for adjusting the position of the picture definition lens ring can be used as an apparatus, coupled to the lens ring, for determining the actual state of the lens ring position according to EP 0 942 305 A1, which apparatus determines the actual position of the lens ring in relation to the lens and converts it into a measurement output signal.
The drive unit for picture definition adjustment can be driven, in accordance with EP 0 574 105 A1, using a control system comprising a plurality of motor units for adjusting the zoom, focus and shutter functions, which motor units are coupled, in accordance with EP 0 575 022 B1, to the lens rings of the camera lens of a motion picture camera and in which position encoders are integrated, and one or more hand-held operating units which can be used to adjust, in an analog and/or electronic fashion, both adjustment values and range limits. The motor units and the hand-held operating unit are connected to one another via a serial control and data bus.
Alternatively, in accordance with DE 196 29 484 A1, the connection between the drive units coupled to the lens rings of the camera lens of the motion picture camera and the position encoders with one or more hand-held operating units for adjusting the zoom, picture definition and shutter functions can be provided via a wire-free control and monitoring of camera functions and thus for adjusting the picture definition, in which a camera-side control and detection unit is connected, via line connections, with a focus, zoom and iris drive unit and which includes a radio modem which transmits control signals to a remote-control unit and receives them from the latter. The operator-side control unit has, for focusing and adjusting the picture definition, a handwheel backed by a scale on which range limits for adjusting the picture definition can be adjusted. A potentiometer connected to the handwheel prescribes absolute values as setpoint values for adjusting the picture definition on the camera lens, which values are transmitted, via the radio transmission link, to the camera-side control and detection unit which adjusts the motor or drive unit connected to the picture definition lens rings to the setpoint position prescribed by the operator-side control unit, in order to adjust the picture definition lens ring.
Since manual focusing can be carried out in specific recording situations only with great difficulty, for example at large or very small distances and with very rapid picture definition variations, it is known from DE 42 05 397 A1, for example, to apply automatic focusing, in which an auto-focusing unit uses an ultrasonic or laser measurement appliance to detect the distance between an object to be recorded and the motion picture camera, and adjusts the picture definition necessary to focus the image to be recorded or the sequence to be recorded on the camera lens of the motion picture camera.
In many applications a change-over from automatic focusing to manual focusing is desired. When switching over from the automatic focusing operation to the manual focusing operation, which may be necessary, for example, if an object to be recorded disappears from the image to be recorded and the picture definition is set to infinity, the problem occurs that the picture definition setpoint value, which was prescribed manually and was adjusted on the manual operating unit, is adopted, which setpoint value deviates from the last setpoint value output by the auto-focusing device to the drive unit for picture definition adjustment, such that intolerable blurring or undesired picture definition shifts result when the automatic focusing operation changes over to the manual focusing operation.